Remove all cygwin CHOST changes

Since #5448 CHOST defaults to cygwin now, so this
is no longer needed.

libqrencode/PKGBUILD

@@ -27,10 +27,9 @@ build() {
   mkdir -p build-${pkgbase}-${pkgver}-${CHOST}
   cd build-${pkgbase}-${pkgver}-${CHOST}
 
-  local CYGWIN_CHOST="${CHOST/-msys/-cygwin}"
   ../${pkgbase}-${pkgver}/configure -C \
     --prefix=/usr \
-    --build=${CYGWIN_CHOST} \
+    --build=${CHOST} \
     --with-tests
 
   make LDFLAGS="${LDFLAGS} -no-undefined"